1. Field of the Invention
This invention relates to a nickel alloy containing small amounts of ruthenium and manganese and, optionally, a small amount of silicon.
Spark plug electrodes, in service, are subject to both corrosion and erosion. The former is caused by chemical attack while the latter is a result of spark discharge. Less effective spark plug performance and eventual spark plug failure can be the ultimate consequences of corrosion and erosion.
2. Description of the Prior Art
Precious metals have been used in a variety of ways to reduce corrosion and erosion of both massive spark plug center electrodes, diameter at the firing end in the vicinity of one tenth of an inch, and fine wire spark plug center electrodes, diameter at the firing end in the vicinity of a few hundredths of an inch. Such precious metals as gold, osmium, iridium, ruthenium, palladium, rhodium, platinum, and the like have been utilized as inserts in less expensive base metal, massive, center electrodes. (See, for example, U.S. Pat. Nos. 3,146,370, 3,407,326, and 3,691,419.) Such electrodes are expensive because they require a relatively large quantity of precious metals in order to achieve a significant increase in service life. Moreover, such electrodes are unduly susceptible to corrosion, particularly at the interface of the base metal and the precious metal. Fine wire center electrodes having firing tips made entirely of precious metals such as ruthenium, platinum, and iridium have been suggested also. (See, for example, U.S. Pat. Nos. 3,315,113 and 3,548,239.) Finally, massive center electrodes coated with an oxidation and erosion resistant metal or metal alloy have been suggested. (See, for example, U.S. Pat. Nos. 3,958,144 and 3,984,717.)
An alloy has been described (U.S. Pat. No. 4,081,710), in which Co or Ni predominates, and is alloyed or compounded with Ru, Rh, Pd, Ir, Pt, Ag or Au or combinations thereof. The amount of precious metal required is disclosed as being between a trace and 20 percent by weight of the alloy. The preferred precious metal is platinum in an amount of 1 to 20 percent by weight.